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1994 Caprice Classic L99
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Discussion Starter · #1 ·
I'm in the middle of replacing the intake manifold gaskets on my 82k engine and the runners and manifold look pretty awful to me.

The point of this post is to ask what you guys would do? What kind of additives and chemicals would you run in the gas and oil? Is it even something to be concerned about? How about the oil on the mating surface? The two passenger side rearmost bolts were covered in oil when I removed them.
The factory sealant was pretty worn to the point the manifold practically pulled itself off when I loosened the bolts so this job was definitely overdue. I will be replacing fel pro intake gaskets with fuel injector o rings and throttle body gasket as well.
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Can always have a machine shop "hot tank" it.
 
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What kind of additives and chemicals would you run in the gas and oil?
Generally, I trust stuff from lubegard.com.
LubeGard has lots of good stuff.
Is it even something to be concerned about?
If you change the oil often enough, and use Chevron with TechRon Fuel System Cleaner, or anything approved by bobistheoilgy.com, you really don't NEED to use additives regularly.
However, whenever I get a new used vehicle in the family, I'll use
Bio/Tech Engine Oil Protectant - Lubegard in the motor oil with Group IV fully synthetic 0W30 ONLY
in cast the previous owner Toyoduhr'd the maintenance.

The rest of the ISSF will surely have plenty of good advice about how to prep the inlet manifold for re-installation, what sealants work best, etc.
 

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All too often overlooked about the LT1 inlet manifold:
There is an entirely separate Idle Air Control inlet manifold hiding in plain sight, running parallel underneath the larger more blatantly obvious passages. (I call it the 'idlespider'.)
When the throttle is (completely) shut, the IAC motor feeds air to these slender paths.

Many LT1 inlet manifolds otherwise thoroughly cleaned, still had over 2 decades of gunk hidden in the idlespider.
For best results, remove that underplate, and don't forget about the EGR and PCV passages as well.
 
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@sherlock9c1 did something before reinstalling the inlet manifold
... something to keep the inlet manifold cooler ...
a barrier? ... a coating ... can't remember ...
 

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First I've heard of this "idle spider" ,but I'm not an engine builder or guru....
 

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First I've heard of this "idle spider", but I'm not an engine builder or guru ...
Even fewer have seen it / noticed it, including many who have removed / reinstalled the inlet manifold.
Close up the front main throttle passages.
Blow smoke through the IAC passages (the spider's head).
The smoke will exit through the spider's legs.
 

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Most of that gunk comes from the PCV system. I always had good success with plain ol' brake cleaner when I was cleaning the inside of manifolds when I was applying epoxy coatings.

On the "idle spider", it's there. if you look into the intake runners, you'll see a small hole in the floor of each runner. The hole connects to the passages below the main manifold. But they're usually not gunked up because the PCV doesn't flow through them.
 

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And where does the PCV connect on a B body ????
Hint , follow the path as it enters the intake below the throttle body.

THIS does not apply to the F body which was routed to the plenum.
Y body , I think was the same as F but not positive.

Build up of crud , reversion and a red hot EGR fed floor do a pretty good job of that , even without the added crankcase fumes.
( ignore my EGR insert as that is a different age old agument)
 

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Noticed significantly less PCV deposits since changing to a "constant orifice" valve instead of old style.
 
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If it makes you feel better my intake looked at least that bad and my lifter valley was worse when I did my intake r/r last year. It was worth the 60 bucks to take it to a local engine shop and have them clean it. I degreased it and painted it after and it came out quite well I think.

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Also definitely take the cover off and the plugs out
There's something I could never find information about regarding the plugs: does it matter if they're fully seated (screwed down as far as they'll go) or not?

When I did my intake, I noticed that the plugs weren't fully seated. So, I re-installed the plugs so that they were at the same depth they were originally, and I also used thread sealer to make sure there wouldn't be any vacuum or exhaust gas leaks.
 

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The plugs don't perform any function on the car. They're there as part of the casting process.
 

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Late to the party -
@Marky Dissod I didn't paint anything. Just keep that oil splash shield in place on the bottom.

@ThreeOfFive - don't play with oil additives, just use a quality synthetic and regular oil changes and it'll clean all the crap out of your motor. I had my intake manifold bead blasted by a local machine shop. For the price, it was worth it. But take out ALL the plugs and fittings before you take it over there, and then thoroughly hose it out with water and then compressed air to get ALL beads out. Then install and seal the plugs with RTV and reassemble. I painted mine with engine enamel and clearcoat while it was out and it looks great.
 

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Late to the party - @Marky Dissod I didn't paint anything.
Just keep that oil splash shield in place on the bottom.
ever taken a look inside your intake? ... one trick I used to make the car more consistent at the track was to coat the inside of the intake with a high temp epoxy ... trying to mimic the plastic LS intake to reduce the intake temps ... sprayed 4 or 5 cans of brake cleaner on the inside ... trying to get all the oil off before ... the epoxy would stick ...

... epoxy worked like a charm. knocked about 2 tenths off my ET compared to before ...
more importantly, it made the car more consistent and less sensitive to heat soak when I was waiting in the lanes ...
Apologies to both shrlock9c1, and stonebreaker.

Point is, while you have it off, no need settle for status quo - maintenance is usually a PERFECT time to upgrade.
 
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Discussion Starter · #20 ·
Excellent information from you all. I ended up putting it back together with just a new gasket but down the road I think I'll once again take it off and clean everything up professionally, or even drop in a 5.7.
 
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